Shell clamping behaviour in the limpetCellana tramoserica

Abstract

SUMMARYThe behaviour of clamping the shell against the substratum may play an important role in the limpet adhesion mechanism because friction generated by this behaviour resists dislodgement by shear forces. This paper describes the development of an apparatus to analyse limpet clamping activity in relation to known forces, including simulated wave activity and predator attack. The results show that Cellana tramoserica clamps its shell in a closely regulated manner consistent with an active role in the limpet adhesion mechanism. Limpets clamped sharply for several seconds in response to single disturbances such as tapping the shell. In response to more continuous disturbance simulating a concerted predator attack, limpets clamped tightly for several minutes. In response to lifting forces applied to the shell, limpets clamped at a set proportion of the lifting force, even if the lift force was a highly dynamic wave profile. This behaviour has implications for numerical models that attempt to describe limpet adhesion because it shows that limpets cannot be represented by a simple mechanical analogue and that the clamping behaviour must be accounted for if useful predictions are to be drawn.

Molecular insights into the powerful mucus-based adhesion of limpets ( Patella vulgata L.)

“…When a predatory attack was simulated, the limpet clamped its shell against the surface, resulting in a rapid decrease in sub-pedal pressure, followed by a less negative pressure as the limpet relaxed slightly but did not quickly return to ambient (taking around 3.7 s to reach 60% of the peak minimum value). This response is similar to the clamping behaviour of Cellana tramoserica reported by Ellem et al, where initial irritation (single tap to the limpet shell or the experimental set-up) caused a clamping force of 2-5 N that decayed in 1-2 s to pre-stressed levels, while continued irritation (continuous tapping) resulted in a much higher force of 25 N that decayed slowly over 5 min [13]. While we measured the sub-pedal pressures and not the forces, we observed a similar sustained decay in response to a simulated predatory attack.…”

“…Numerous studies have sought to understand the principles behind the limpet's powerful attachment by ascribing it to suction [5,11,12], clamping [13] or glue-like secretions [11,14,15]. Smith reported a significant reduction in sub-pedal pressures when limpets (either Tectura scutum or Lottia gigantea) were placed on an acrylic surface and slid across the pressure gauge (approx.…”

“…Despite over a century of research, the mechanisms responsible for the patellid limpets' strong attachment remain unresolved [4]. So far, proposed ideas include: suction [5,11,12] (lowering of pressure beneath the attachment organ by muscle contraction), clamping (muscles forcing shells against the substrate to provide additional friction) [8,13], viscous adhesion (resulting from the flow resistance of viscous secretions beneath the pedal sole) [4] and glue-like adhesion (via secretions that form chemical interactions to link the pedal sole with the surface) [11,14,15]. Following a series of studies ruling out suction in Patella [4,6,14], suction as a potential mechanism of attachment was re-introduced in a distantly related family of limpets, Lottidae [5,12].…”

Biorobotic adhesion in water using suction cups

“…They have immense adhesive power and are sometimes used by people in the tropics to catch sea turtles by attaching a fishing line to their tails. Similar 'super suction' release forces of up to 25 N have been reported for limpets, which weigh less than 25 g [7]. Animals use mechanisms such as suction adhesion [11,18,21], capillary adhesion [17] and mechanical devices (such as minute toothed plates) to attach to a surface or another animal.…”

<strong></strong>Convergent Evolution of Attachment Mechanisms in Aquatic Animals

“…In barnacles (Arthropoda) the retractor muscle pulls the peripheral shell plate downward at the time the permanent cement is secreted, thereby improving adhesion (Kamino 2016). In limpets, the contraction of the powerful foot muscle clamps the shell against the substratum, playing an important role in the adhesion mechanism because friction generated by this behavior resists dislodgement by shear forces (Ellem et al 2002). Meanwhile, in reversibly attaching animals lacking a duogland system, detachment is mostly achieved through mechanical forces (Lengerer and Ladurner 2018) (see also Section III).…”